Mammalian, and notably human joints, are subject to damage notably from trauma and disease. Both repetitive micro-trauma with occurrence more frequently than a capacity for healing and macro-trauma with significant immediate damage which cannot be recoverable by healing can lead to advancing bone damage. Early stage joint trauma and disease which are not healed typically can lead to a spectrum of pathological conditions of minor joint damage, advancing bone damage, degenerative joint disease and osteoarthritis.
Mammalian joints characteristically join a first bone member to a second bone member and include diarthrodial joints particularly those in which load bearing contiguous bone surfaces of each of the first and second bone members are covered with articular cartilage forming a respective margin of each of the first and second bone members. The contiguous bony surfaces of the surfaces which are normally in contact during movement of the joint are to be contrasted with non-contiguous surfaces of the bone members being surfaces which are not normally in contact during movement of the joint. The articular cartilage is provided as an outer layer over the sub-chondral bone, that is, the bone underlying the cartilage on the condyle at the end of the bone member. A condyle is a round projection or rounded articular area which can generally be characterized as a load bearing surface of a bone member. Articular cartilage is very poorly vascularized and, when damaged by trauma or disease, heals extremely slowly.
Most mammalian joints have, in addition to merely opposing bone members and their cartilage, synovial membranes which may provide synovial fluid proximate or intermediate the bearing surfaces and many joints are also provided with, to be divided completely or incompletely, by an articular disk or meniscus typically provided intermediate opposing articular cartilages.
Joint traumas and disease include damage and disease to the synovial membranes and the articular disk and meniscus if present which lead towards destruction and tearing away of the articular disks or meniscus and subsequent damage to the articular cartilage and subsequent bone to bone contact and damage to the sub-chondral bone.
Presently existing techniques for treating advancing bone damage include firstly biological resurfacing for early stages of the bone damage and, secondly, prosthetic replacement for late stages of bone damage. Biological resurfacing techniques for reconstituting the cartilage include debridement, abrasion arthroplasty, drilling, microfracture techniques, autologous chondrocyte transplant techniques and stem cell seeded transplants. Biological resurfacing has numerous disadvantages and is often unsuccessful, notably due to the fact that cartilage is not vascularized, heals extremely slowly and due to the fact that loading to which the cartilage is subjected due to normal use of the joints destroys the cartilage. Thus, biological resurfacing techniques have a high failure rate. Dilemmas which face biological resurfacing include the requirement that joints must move to remain functional yet movement destroys the new cartilage and prevents new cartilage formation. Thus, only extensive protracted and functionally limited rehabilitation is available which results in significant health care and social costs.
Prosthetic replacement is a treatment technique in which, for example, the entire articular cartilage and sub-chondral bone is replaced by a synthetic member. Typically in prosthetic replacement, as for example in the hip which comprises a ball and socket type joint, the ball on one bone member is completely removed and replaced by the synthetic ball and the interior surface of the socket on the other bone member is completely replaced by a new synthetic socket. Prosthetic replacement suffers significant disadvantages that a patient suffers while its natural joint deteriorates to a sufficient extent that surgery is necessary; the surgery is expensive; and the surgery is biologically destructive and irreversible. Moreover, the new joint is destined to failure after a period of time. Huge health care and social costs are associated with prosthetic replacement.